1. Field of the Invention
This invention relates to tire inspection and particularly to the inspection of tire beads.
With the growing use of radial tires, it is believed that bead loads will generally be higher with radial tires than with conventional tires. Tire beads perform in a cyclic stress, or fatigue limited environment. The increased retreading of radial tires is apt to result in the use of tire beads over two or more life cycles under cyclic stress conditions somewhat greater than would be the case with the prior bias ply tires. Therefore, bead inspection techniques are of considerable prospective value to the retread industry and for the safety of users of retreaded tires.
2. Description of the Prior Art
For many years there have been only two practical bead inspection techniques available to the pneumatic tire industry. The first of these is hand and visual inspection, which has been developed to a relatively high degree of skill by trained tire inspectors. Nevertheless, in many cases, they are unable to find internal defects, particularly relatively small ones. Therefore, many tire companies have relied on a second inspection, that of X-ray or fluoroscopic examination of tires to determine the internal characteristics of tire beads. Prior suggestions for tire inspection machines included the use of infra-red detectors, holography, X-rays, ultrasonics, and vibrational resonance.
In addition, references may be made to various patents which disclose automatic tire inspection machines, which, however, do not involve bead inspection. These are U.S. Pat. No. 3,130,957 granted Apr. 28, 1964 to Branick; U.S. Pat. No. 3,540,697 granted Nov. 17, 1970 to Matteuzzi; U.S. Pat. No. 3,157,387 granted Nov. 17, 1964 to Pinter et al; U.S. Pat. No. 3,542,340 granted Nov. 24, 1970 to Peisl; U.S. Pat. No. 3,550,443 granted Dec. 29, 1970 to Sherkin; U.S. Pat. No. 3,602,045 granted Aug. 31, 1971 to Ternau; and U.S. Pat. No. 3,621,246 granted Nov. 16, 1971 to Horsey et al.